package com.transfer.utils;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.security.DigestInputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class MD5FileUtil {
    
    private static final Logger logger = LoggerFactory.getLogger(MD5FileUtil.class);

    protected static char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6',
            '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
    
    public static String fileMD5AndCanSuspend(File inputFile,boolean suspending) throws IOException {
      // 缓冲区大小
      int bufferSize = 256 * 1024;
      FileInputStream fileInputStream = null;
      DigestInputStream digestInputStream = null;
      try {
         // 拿到MD5转换器
         MessageDigest messageDigest =MessageDigest.getInstance("MD5");
         // 使用DigestInputStream
         fileInputStream = new FileInputStream(inputFile);
         digestInputStream = new DigestInputStream(fileInputStream,messageDigest);
         // read的过程中进行MD5处理，直到读完 文件
         byte[] buffer =new byte[bufferSize];
         while (!suspending&&digestInputStream.read(buffer) > 0);
         // 获取MessageDigest
         messageDigest= digestInputStream.getMessageDigest();
         if(suspending)
           return null;
         // 拿到结果，也是字节数组，包含16个元素
         byte[] resultByteArray = messageDigest.digest();
         // 同样，把字节数组转换成字符串
         return bufferToHex(resultByteArray);
      } catch (NoSuchAlgorithmException e) {
         return null;
      } finally {
         try {
            digestInputStream.close();
         } catch (Exception e) {
         }
         try {
            fileInputStream.close();
         } catch (Exception e) {
         }
      }
   }
    public static String fileMD5(File inputFile) throws IOException {
          // 缓冲区大小
          int bufferSize = 256 * 1024;
          FileInputStream fileInputStream = null;
          DigestInputStream digestInputStream = null;
          try {
             // 拿到MD5转换器
             MessageDigest messageDigest =MessageDigest.getInstance("MD5");
             // 使用DigestInputStream
             fileInputStream = new FileInputStream(inputFile);
             digestInputStream = new DigestInputStream(fileInputStream,messageDigest);
             // read的过程中进行MD5处理，直到读完 文件
             byte[] buffer =new byte[bufferSize];
             while (digestInputStream.read(buffer) > 0);
             // 获取MessageDigest
             messageDigest= digestInputStream.getMessageDigest();
             // 拿到结果，也是字节数组，包含16个元素
             byte[] resultByteArray = messageDigest.digest();
             // 同样，把字节数组转换成字符串
             return bufferToHex(resultByteArray);
          } catch (NoSuchAlgorithmException e) {
             return null;
          } finally {
             try {
                digestInputStream.close();
             } catch (Exception e) {
             }
             try {
                fileInputStream.close();
             } catch (Exception e) {
             }
          }
       }
    /**
     * 获取文件�?MD5
     * @param file 文件
     * @return MD5 �?
     * @throws IOException
     */
    public static String getFileMD5String(File file) throws IOException {
        MessageDigest messagedigest = null;
        try {
            messagedigest = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            logger.error("MD5FileUtil messagedigest初始化失败", e);
        }
        FileInputStream in = new FileInputStream(file);
        FileChannel ch = in.getChannel();
        MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY, 0,
                file.length());
        messagedigest.update(byteBuffer);
        return bufferToHex(messagedigest.digest());
    }

    private static String bufferToHex(byte bytes[]) {
        return bufferToHex(bytes, 0, bytes.length);
    }

    private static String bufferToHex(byte bytes[], int m, int n) {
        StringBuffer stringbuffer = new StringBuffer(2 * n);
        int k = m + n;
        for (int l = m; l < k; l++) {
            appendHexPair(bytes[l], stringbuffer);
        }
        return stringbuffer.toString();
    }

    private static void appendHexPair(byte bt, StringBuffer stringbuffer) {
        char c0 = hexDigits[(bt & 0xf0) >> 4];
        char c1 = hexDigits[bt & 0xf];
        stringbuffer.append(c0);
        stringbuffer.append(c1);
    }

    public static void main(String[] args) throws IOException {
        long begin = System.currentTimeMillis();

        File big = new File("C://mywork/test.txt");
        /*String md5 = getFileMD5String(big);*/
        String md5 =fileMD5(big);
        long end = System.currentTimeMillis();
        System.out.println("md5:" + md5);
        System.out.println("time:" + ((end - begin) ) );

    }

}